Not sure which of the Volvos in your sig this thread refers to, but your mention in the original post of the "larger" of the two filaments had me wrinkling my brow. Larger how? Length? Girth? The one that should be showing oncoming traffic your intentions is the one larger in girth, but smaller, usually, in length. That is the 21W filament. The skinny one is for the parking or "running" light, at 5W.
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Art Benstein near Baltimore

A marine biologist developed a race of genetically engineered dolphins that could live forever if they were fed a steady diet of seagulls. One day, his supply of the birds ran out so he had to go out and trap some more. On the way back, he spied two lions asleep on the road.

Afraid to wake them, he gingerly stepped over them. Immediately, he was arrested and charged with...transporting gulls across sedate lions for immortal porpoises.